With the gradual progress of display technologies, assistance of displays can make life of people more convenient. To achieve attributes of small weight and small thickness of displays, flat panel displays (flat panel display; FPD) have been prompted to become current mainstreams. In a variety of flat panel displays, liquid crystal displays (liquid crystal display; LCD) have advantages such as high space utilization efficiency, low power consumption, no radiation, and low electromagnetic interference, and therefore liquid crystal displays are well received by consumers.
In general liquid crystal displays, an active element array substrate integrated with a color filter film (Color filter On Array; COA) and an active element array substrate integrated with a black matrix (Black Matrix On Array: BOA) have become current mainstreams. For the current COA substrate or BOA substrate, an issue of mis-alignment between a color filter film and a film under the color filter film on a same substrate generally affects the display quality and product yield. How to quickly determine whether there is a mis-alignment issue and determining whether the mis-alignment degree is within a tolerable range is one of topics concerned by designers.